English to German Tech/Engineering Geology mining

This is from an article explaining the porspecting and exploration of gold mines:
I've checked Langenscheidt FWB Technik, Ernst, Benz-Wessels and numerous on-line geological dictionaries, to no avail. I've come across various forms of "Tonnagen", even "Bulk Tonnagen" but would like to make sure that there is indeed no other proper German term before I use 'Bulk Tonnage'.


"**Bulk-tonnage** deposits typically have low grades over long intervals, while underground projects have higher grades over narrower intervals. Some vein-type deposits have bonanza grades, but caution should be exercised, as these veins often pinch and swell, or disappear altogether. To prove up reserves, vein-type deposits must be drilled on a tighter grid than **bulk-tonnage** deposits with evenly disseminated mineralization."

TIA!